The present invention relates to improvements in safety caps for a cannula. The invention pertains to a safety cap for a cannula, consisting of an outer sleeve of a rigid plastic component and a seal element of a gas permeable, flexible plastic component, held in the outer sleeve. The seal element is provided with a channel, closed at one end, for sealing the opening at the tip of the cannula.
Safety caps of this type are used in the medical field and have already been known for a long time for cannulas and for syringes equipped with cannulas. Their purpose is to make it possible for the cannulas to be packaged under sterile conditions without damage to the packaging material and to reduce the risk of injury during handling. In addition, the safety caps serve to prevent damage to the thin, bevel-ground tips of the cannulas. On occasion, the safety caps are also replaced on the cannulas after use.
Before they are used, the safety caps from production must first be sterilized. The cannulas and the syringes must also be sterilized. This is done with gaseous media such as steam or ethylene oxide gas (ETO). The items mentioned are usually used only once and then discarded in order to prevent the transfer of disease. In view of the large quantitative demand for these items, therefore, it is very important that it be possible to produce them easily and rapidly. The way in which these items are designed, however, must always take into account the goal of minimizing the risk of injury and infection.
According to the invention, a safety cap for a cannula which has an outer sleeve of a rigid plastic component and a seal element of a flexible plastic component held in the outer sleeve to seal off the opening at the tip of the cannula is described in DE 4,234,319 A1. This cap is produced by a two-component injection-molding process. The known safety cap, however, is still in need of improvement with respect to sterilization and handling.
The known safety cap for cannulas is sterilized before use. Because the rigid plastic component of the outer sleeve is impermeable to gas, however, the gaseous sterilizing medium can reach the interior areas only with difficulty. These caps must therefore be held for a long time in the sterilizer to ensure that all the germs and pathogens are killed. In this respect, sterilization in the ready-to-be-packaged state with the cap set in place on the cannula is even less favorable. Because the goal has always been to meet the highest sterility standards, so far little or no attention has been given to reducing the time it takes to sterilize the caps.
The outer sleeve made of rigid plastic gives the known safety cap sufficient rigidity toward the outside, whereas the seal element of flexible plastic seals the opening at the tip of the cannula. To minimize the risk of injury and infection, the outer sleeve extends continuously and without a break over the entire length of the exposed area of the cannula to be protected. The safety cap is connected to the syringe exclusively by the flexible component, and at the insertion opening the safety cap consists entirely of this flexible component. Nevertheless, the flexible design of the insertion opening of the safety cap has certain disadvantages with respect to the reliability with which the cap can be gripped when the cannula is being reinserted into the cap, because the cap can easily be squeezed in too much.
The invention is therefore based on the task of creating a safety cap for a cannula which can be produced efficiently and handled safely and which is characterized by excellent sterilization behavior.
This task is accomplished by a safety cap of the general type described above in which the outer sleeve is interrupted by at least one lateral opening on the long side between its bottom end and its top end.
As a result, it become possible to sterilize the safety cap effectively and quickly even after it has been placed on the cannula. The route taken by the gaseous sterilization medium into the interior of the safety cap is considerably reduced by the openings provided in the side of the outer wall of the cap. Furthermore, in cases where both parts are sterilized simultaneously with the safety cap in place on the cannula, there is no longer any need for the insertion opening of the safety cap to be made of flexible plastic to allow the entry of the gas. This also leads to the possibility of a design which offers improved handling.
In accordance with an advantageous design, the bottom end of the outer sleeve has an essentially cylindrical base section, possibly tapering slightly toward the top end, with an insertion opening for the cannula profiled tope section is disposed adjacent to the base. Parts of the profiled top section following in the longitudinal direction of the safety cap have a cross section which is not round on the outside. This top section extends all the way to the top end of the outer sleeve. The safety cap is thus reliably prevented from rolling away when it is not attached to the cannula, which improves the handling aspect. That the safety cap for the cannula can be counted on to stay put also helps indirectly to reduce the spread of infection, because the possibility is reduced that the cap could fall to the floor, be picked up, and be put back on the cannula, a situation which could allow the syringe to be used again in error.
In accordance with another advantageous of the invention, the outer sleeve has a pass-through opening for insertion feature, the seal element and which is sealed off at the top end of the outer sleeve by the seal element. Each of the lateral openings is located in a section of the outer wall of the outer sleeve which has been recessed in the direction of the pass-through opening through the outer sleeve. Thus, the lateral openings lie outside the direct gripping area of the outer wall. It is known that cannulas are beveled off at the free end, so that the end of the cannula has a taper in contrast to the main tubular section itself. The end of the cannula can therefore penetrate relatively easily into a plastic body or even pass through it completely if the plastic is thin-walled. The tubular section, however, offers greater resistance to complete insertion or penetration. As a result of the design measures described above, the danger of injury, especially in the area of the lateral openings of the outer sleeve, is avoided in the event that the safety cap is mistakenly pushed slantwise onto the cannula. Accordingly, even if the tip of the cannula passes through the outer sleeve, it cannot extend far enough to reach the fingers of the person handling the cannula. The depth of the recessed area will thus preferably be calculated in such a way that the tip of the cannula will still be within the recess at the time the tubular section with its larger cross section reaches the sleeve and the resistance to penetration thus starts to increase significantly.
To simplify production in an injection-molding process, it is advantageous for the recessed section to extend in the longitudinal direction of the outer sleeve, so that no undercuts are formed.
It has been found that providing lateral openings large enough for sterilization does not significantly increase the risk of penetration of the outer wall by the needle. In a further elaboration of the invention, an especially reliable solution is obtained by providing the edge of the lateral opening which is at the top in terms of the insertion direction of the cannula with an outward-projecting safety tongue, the inside wall section of which slants inward toward the top end of the outer sleeve. If for some reason the safety cap is pushed onto the cannula at an extreme slant, the cannula will strike this wall section of the tongue, which more effectively prevents the outer sleeve from being penetrated. The slant of the tongue deflects the cannula, which has been inserted at a slant, back into the correct position. In addition, the outward-bent form of the protective tongue makes it possible to enlarge the lateral opening without any loss of safety. Accordingly, a large entry region for the sterilizing medium can be created, which brings about a further improvement in the sterilization behavior.
In accordance with another advantageous embodiment of the invention, the top section has an essentially cylindrical base element, possibly tapering slightly toward the top; this base element is provided with four ribs, each of which begins at the base and extends in the longitudinal direction of the safety cap. This design combines ease of production by injection molding with the ability to prevent the cap from rolling away in the loose state; at the same time, the ribs also provide high structural rigidity.
A shape which is especially easy to grip is obtained when each of the ribs is oriented at a slant with respect to the radial direction of the outer sleeve in such a way that the top section acquires a cross section in the form of an xe2x80x9cHxe2x80x9d. In this case the wide, flattened outer flanks of the H offer a relatively large contact surface for the fingers of the person handling the cap, who can thus grip the cap securely and guide it to the cannula with the correct orientation.
It is preferable here for each of the lateral openings to be located in a section of the wall between two essentially parallel ribs. As a result, a shape is obtained which has high safety potential with respect to the risk of injury, because the recessed area offers a high degree of protection in the event that the cannula penetrates the safety cap in the weakest area of the outer wall, namely, the lateral openings in the outer sleeve.
The lateral openings are preferably directly adjacent to the base section, that is, to the area which tends to have the greatest wall thickness, so that the weakening of the rigidity of the outer wall associated with the lateral openings is minimized. In addition, the lateral openings thus become located approximately in the middle of the cap, seen in its longitudinal direction, so that the route taken by the sterilization medium into the cap remains short, as a result of which the sterilization behavior is further improved.
In yet another advantageous embodiment of the invention, the lateral openings in the outer sleeve are covered on the inside by the seal element. Thus, the safety cap acquires a closed external form with respect to the cannula, so that, after the syringe has been filled and a sterile cannula with its safety cap has been set in place, any danger of contamination to the cannula is excluded, especially in cases where the content of the syringe is not injected immediately thereafter.
So that the seal element will be held securely in the outer sleeve, the top section is provided in an advantageous embodiment along its inside wall in the area of each of the lateral openings with a groove extending in the longitudinal direction of the outer sleeve. These grooves are open at the end facing the base, and the seal element is provided with radial projections which fit into the grooves and preferably fill them completely.
In accordance with another advantageous design, the bottom end of the outer sleeve is designed as a collar, which surrounds the insertion opening and extends essentially in the radial direction. This serves as to protect the fingers when the cap is being replaced on the cannula and can also serve as a stop, which strikes a cone provided on the cannula or on the end of the syringe and thus prevents the cap from being pushed on too far and top end from being penetrated. As a result, the overall length of the cap can be reduced, which has the effect of conserving material without impairing its safety function.
The collar is preferably designed as a cone pointing toward the top end, so that, if the person handling the cannula misses the insertion opening and the tip of the cannula thus strikes the collar, the tip is prevented from slipping off toward the finger holding the cap. Instead, the slightly conical shape has the effect of redirecting the path of the cannula toward the insertion opening.
Yet another advantageous design makes it easier to set the safety cap down onto the cannula, in that the closed channel of the seal element is designed with a continuous taper at the beginning, pointing toward the closed end; this tapered part is then followed by an end section, into which the opening at the top of the cannula penetrates in the fully inserted state, the inside diameter of this end section being smaller than outside diameter of the tubular section of the cannula. As a result, the cannula can first be introduced freely into the bottom end of the cap, where the tapered section of the channel in the seal element is able to correct the direction in which the cannula is being inserted, if necessary. Then, toward the end of the insertion movement, the opening of the cannula becomes tightly enclosed by the seal element. Thus the desired seal effect is obtained in addition to elastic support for the top end of the cannula, which is protected from damage as a result.
In yet another advantageous design of the invention, the handling of the safety cap is improved even more by providing the section at the top of the longitudinal axis of the cap with two opposing narrow sides and two opposing wide sides, each of the latter being designed as gripping surfaces provided with anti-slip projections and/or depressions and/or holes.
The top section, furthermore, can be designed with a cylindrical base body which tapers conically toward the top end with ribs extending in the longitudinal direction of the safety cap. This conically tapering base body has several lateral openings between each pair of adjacent ribs, these openings being designed as elongated slots oriented crosswise to the longitudinal direction of the safety cap. The slots are filled with the material of the flexible plastic component. With this advantageous design, an excellent sterilization behavior is obtained, because the penetration routes of the sterilizing medium can be kept very short. The slot-like shape of the lateral openings offers only very small surface areas vulnerable to attack by the tip of cannula and thus minimizes the chance that the cannula could unintentionally penetrate the outer wall of the safety cap, but at the same time this shape guarantees optimum accessibility to the sterilizing medium. Because the slots are filled with the flexible component, an almost completely smooth outward appearance is obtained. This means that is impossible for any random objects that may be lying about to hook onto the slots and unintentionally pull the cap off the cannula. If the filler material is provided with a nubbly, outward-curved surface, it is also possible, if desired, to create slip-proof gripping areas.
So that the cannula safety cap can be produced efficiently, it is preferable to design it as a two-component, injection-molded part.